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Tropical Ecology 43(1): 49-59, 2002 ISSN 0564-3295 © International Society for Tropical Ecology

Remote sensing application in

D.P. RAO

National Agency (NRSA), Hyderabad

Abstract: India has made tremendous progress in the aerospace technology in the last two decades. We are one, among the worlds best in and the remote sensing technology. We are also one of the developing countries facing the natural disasters and trying level best to mitigate their ill effects. At the best we can minimize their effect. To achieve this, we need to have a comprehensive management program dealing with mapping and monitoring. The re- mote sensing technology with the fieldwork provides an edge to characterize the geomorpho- logic aspects. The present paper reviews the application of the remote sensing tools in the ap- plication of geomorphology. A few case studies from the different part of the country are pre- sented in the context of geomorphology of the foothills of Siwaliks, Central India and the east- ern coast and use of remote sensing.

Resumen: En las últimas dos décadas la India ha hecho un enorme progreso en la tec- nología aeroespacial. Estamos entre los mejores en tecnología satelital y de percepción remota a nivel mundial. También somos uno de los países en vías de desarrollo que enfrentan desas- tres naturales y que intentan amortiguar sus efectos negativos. En el mejor de los casos po- demos minimizar su efecto. Para conseguirlo, necesitamos contar con un programa de manejo de gran alcance relacionado con la elaboración de mapas y el monitoreo. La tecnología de percepción remota, en combinación con el trabajo de campo, ofrece ventajas en la caracterización de los aspectos geomorfológicos. El presente artículo revisa la aplicación de las herramientas de percepción remota a la geomorfología. Se presentan algunos estudios de caso de diferentes partes del país en el contexto de la geomorfología de las estribaciones de sierra en Siwaliks, India central y la costa oriental, y del uso de la percepción remota.

Resumo: A Índia fez um enorme progresso na tecnologia espacial nas últimas duas déca- das. Ela situa-se entre as melhores na tecnologia de satélite e detecção remota. Ela é, também, um dos países em desenvolvimento que enfrentam desastres naturais e fazendo o seu melhor para mitigar as suas consequências negativas. No melhor dos casos ela pode minimizar os seus efeitos. Para atingir este nível, é necessário dispor-se de um programa integrado de gestão que integre o mapeamento e a monitorização. A tecnologia de detecção remota, associada ao tra- balho de campo, proporciona um avanço na caracterização dos aspectos geomorfológicos. Este artigo revê a aplicação dos instrumentos de detecção remota na geomorfologia. Alguns estudos de casos do uso da detecção remota são apresentados em diferentes regiões do país no contexto da geomorfologia da base das colinas de Siwaliks, Índia Central e na Costa Oriental.

Key words: Geomorphic mapping and analysis, geomorphology, , remote sensing.

Introduction matter consists of two disciplines, remote sensing and geomorphology. Remote sensing which is, As the title of the article indicates, the subject primarily based on principles of physics, is the sci- 50 GEOMORPHOLOGY ence and art of acquiring information about an ob- derstanding of various processes leading to land- ject or phenomena without physically coming in forms is necessary to understand the environment contact with it. Geomorphology is the science of in which we live. Remote sensing is an effective study of the of the earth. Both the dis- tool in this understanding, as aerospace images ciplines are exhaustingly covered in literature contain integrated information of all that is on the (Fairbridge 1968; Lillesand & Kiefer 2000; Sabins ground, the landform, the ecology, the resources 1997 & Verstappen 1977). Remote sensing obser- contained in the area and the impact of human vations from aerial and space platforms which are actions on the natural landscape. The dynamism currently in operation provide a synoptic view of with which changes occur in the landscape is terrain features in images which are interpreted brought out effectively by repeated coverage of im- by thematic specialists to understand and extract ages of the same area at different times. Images information of specific interest from the images. convey many things even to the untrained eye and Formal training is required for interpretation to for a professional it conveys much more including understand the significance of image elements con- many features hitherto unknown or unseen on the tained in the image in addition to formal education ground. in the theme speciality. Geomorphological map- ping from satellite and aerial images for example, Geomorphology - basic concepts needs a thorough knowledge of the subject geo- The earth’s surface forms are primarily due to morphology, i.e., how certain natural and man- hypogene or endogenous processes, which include made processes lead to landforms. Since the most diastrophism, leading to geologic structure, tec- data are essentially recorded in digital tonic activity and leading to volcanic form without a stereoscopic coverage, generated landforms. These forms are modified by epigene or images are two-dimensional. Geomorphological exogenous processes, which include and analysis of surface forms of the earth is a direct depositional activities of water, wind and ice. form of interpretation from space images. Aerial Other activities include , mass wasting photos with required forward overlap usually pro- or movement of material by gravitational action, vide the third dimension of height, which adds to land-ocean interaction resulting in landforms due the precision of interpretation including mor- to waves, currents, tides and . Climate is phometry. another important factor, which has relevance in Geomorphology as a science developed much shaping of the earth’s surface because the proc- later than although several aspects of esses that act upon the surface material are differ- geomorphology are embedded in geological proc- ent in different climatic zones (Van Westen 1994). esses. Geomorphology deals with the genesis of For example, limestone forms hills in a dry climate relief forms of the surface of the earth’s crust. Cer- whereas in wet climate, it forms Karst tain natural processes are responsible for the with sink holes, caves and caverns predominating forms of the surface of the earth. A thorough un-

Table 1. Landform processes.

Process Form (of varying scales) Local (Example) Regional (Example) Tectonic/Structural Anticlinal Hill and synclinal valley First order folded mountain systems Volcanic Cone, Crater, Lava tunnel Volcanic fields Denudational Pediment-inselberg topography Denudational Hills, pediplains Fluvial (Riverine) Alluvial fan, slough, Terrace/Oxbow Deltas, flood plains, Alluvial plains Marine Beach ridge, terrace, lagoon, spit, bar Coastal plain Glacial Cirque, drumlin, esker, moraine ridge Outwash and moraine plains, glacial valleys Aeolain Sand dune, yardang Dune fields Solution Sink hole Karst topography Antheropogenic Quarry, mine dump Urban sprawls, mine fields

RAO 51 because of its susceptibility to solution activity. The most comprehensive geomorphological Similarly, granite stands out as hard in non- survey method is the one evolved by ITC (Verstap- tropical areas whereas in the tropics it undergoes pen 1977) which resulted in three different kinds deep chemical weathering and becomes a soft rock. of maps: Analytical geomorphological map, syn- It is also understood that climate has strong influ- thetic geomorphological map and pragmatic (ap- ence on vegetation which in turn has relationship plied) geomorphological map. Analytical geomor- with landforms. Landforms and plant ecology thus phological maps are applicable for mapping at all form a sound combination; a change in plant ecol- scales and serve as a basis for applied geomor- ogy may have significance in change in landform phological mapping. The informations contained and vice-versa, although human influence on vege- in these maps include tation may disturb the relationship. Time is an- (a) morphogenesis i.e. the terminology should other important factor that may preserve or de- indicate the process/ gneisses (e.g. alluvial stroy the natural landform, because it controls the fan, piedmont); stage in the sequence of processes leading to forms. (b) morphostructure/. Usually the At any given time, the more recent processes and underlying bedrock and structure will have the resultant forms dominate the landscape. The a profound influence on the landform (e.g. Pleistocene to Holocene glacial cycles with inter- structural hill, granitic residual hill etc.); vening interglacial periods i.e. cold and warm cy- (c) morphometry i.e. quantitative information cles have modified the surface forms throughout about relief e.g. height of terrace, slope an- the world and many of the forms of the present day gle etc; are a result of these cycles. It is generally consid- (d) morphochronology i.e. different ages of ered that most forms are not older than Tertiary landforms whenever such information is and there are some relict forms of pre-Tertiary pe- available. riod. Synthetic geomorphological maps contain, in addition to four levels of terrain mapping units, Classification of landforms also contain additional environmental information In order to understand the landforms system- required of every terrain mapping unit gathered subsequently on the basis of number of site obser- atically in the context of the origin of landforms, a vations in every unit. These observations include, genetic classification is generally accepted as most appropriate. Table 1 shows the major natural for example, , hydrology, vegetation/ land use/ landcover and topography. These data are pre- processes, which result in various forms with a few sented in tables or use of GIS can be made to indi- typical examples at local and regional scale. cate each theme as a spatial layer. Geomorphological mapping Pragmatic or applied geomorphological maps can be derived from analytical and synthetic maps. The first geomorphological map prepared in Maps related to natural hazard assessment and 1914 but the main demand for the maps came developed for mitigation programs are increasingly cover form planner and agronomists after World becoming useful, as hazard zoning which has a War II. However, a formal mapping system was direct bearing on geomorphology is possible in all designed only during 1950s. Many systems were cases. Maps on flood hazard zoning, mountain developed by European countries like France, Po- hazard zoning, drought hazard zoning, land and Russia. The International Geographical hazard zoning, volcanic hazard zoning, cyclone Union’s Sub-commission on geomorphological hazard zoning are some typical examples of prag- mapping was set up in 1960 to standardize legends matic geomorphological maps (Verstappen 1977). for mapping. However, specific consensus was ar- Other applied geomorphological mapping examples rived at a modified legend. A geomorphological include maps for and hydrocarbon explo- map must give information about morphology (ap- ration , which contains geomorphic anomalies in- pearance), morphometry (dimensions and slope dicative of suitable subsurface structures. For ex- values), morphogen (origin/genesis) and morpho- ample, incipient radial drainage or compressed chronology (the age) of each form. Representation meanders may indicate active buried structures of these details is an involved and complicated suitable for mineral/ hydrocarbons. Similarly high matter on a single map. recharge zones (piedmont), disappearing drainage 52 GEOMORPHOLOGY lines and discharge zones indicated by sudden ap- same site at regular intervals of time which varies pearance of vegetation throw light on ground wa- depending upon the orbit height, inclination etc. ter exploration. Anomalously displaced terraces The following are specific advantages of satellite and alluvial fans (Rao 1977, 1978), indicative of images for deriving information on ground fea- neotectonic activity changing river courses leading tures, some of which are dynamically changing, to anomalous lakes (Rao 1975) and study of Pa- like land use. leodrainages, indicative of climatic and tectonic activities all have immensely benefited in under- Multi temporal capability standing the phenomena through the knowledge of Indian Remote Sensing satellite (IRS) at a geomorphology. height of about 800 km, revisits every 22 days the Traditionally geomorphological mapping has same site; any change occurring between two suc- been in practice ever since aerial photos became cessive visits becomes evident in the image. While available. Landforms have been the direct object no change occurs in major landforms in the short of interpretation of aerial photos and these are in- period, the changes brought about by disasters like terpreted in terms of other themes like geology, floods, cyclones, change in river courses, soils etc. Inductive and deductive reasoning is re- erosion of the river banks etc., can be automati- sorted to for interpretation of soils, for example, as cally detected. Additionally, landuse/ land cover pedological information is not directly seen and it changes, which are dynamic, highlight certain has to be extracted from terrain feature like land- landforms during some seasons of the year. forms, geology, vegetation, drainage etc. Multi spectral capability Remote sensing application Most remote sensing satellites have sensors, Remote sensing as described earlier is sensing which record, not only in visible band but also in from a distance. The electro magnetic energy after NIR, SWIR and MIR bands apart from thermal interacting with matter can be recorded by a sen- band in selected satellites. recording sor and the recorded data can be seen as an image requires special effort and usually such satellite or photo depending upon the sensor. The electro- are exclusive. The advantage in multispectral ca- magnetic spectrum is a continuum of energy that pability is that certain bands or a combination of ranges from meter to nanometers in bands provide better contrast for image interpreta- and travels at the . The spectrum tion than other bands. The interpreter has to be has several windows through which reflected or knowledgeable to choose a particular sensor data emitted radiation is recorded in sensors (Sabins depending upon the specific application. Unlike in 1997). Among the sensors are aerial , aerial photos where visual interpretation is com- which employ a film for recording in visible (B&W mon, satellite multispectral data have an advan- and color) and near band. Data from visi- tage in that the image data in various bands can ble, near infrared and other optical windows are be subjected to digital enhancement techniques for recorded by multispectral scanners. Thermal highlighting contrasts in objects for improving im- scanner records thermal (emitted) radiation. Ac- age interpretability (Sabins 1996). Also, because tive microwave sensors (SLAR or SAR) record of large volume of digital data, digital techniques data from microwave region of spectrum and have are the only means to handle data for selecting the advantage of recording day and night as well and analysing to extract required information as through clouds. Thus technologically it is pos- quickly. While digital analysis is faster and ap- sible to record terrain information by various sen- propriate in identification and delineation of crops sors. and land use where each land use/land cover may have unique signature, landforms can be best in- Advantages of remote sensing terpreted on the basis of analysis of basic elements Remote sensing satellites by virtue of their or- of interpretation outlined earlier namely tone, tex- biting in a sun synchronous orbit and crossing the ture, size, shape, relief, drainage, slope, land use equator at the same local time, capture the images and association of features. Verstappen (1977) of the terrain with the same illumination and pro- describes four phases of image interpretation vide repetitive coverages i.e. satellites revisit the namely: RAO 53

(i) detection, (ii) recognition and identification, be integrated to decide the optimum spatial resolu- (iii) analysis and (iv) classification of observable tion data. features in terms of landform and genesis. A good reference level in the subject plus a Microwave remote sensing in geomorphic analysis formal training in interpretation are essential to In contrast to optical remote sensing, be- derive maximum information from image. ing an active sensor provides all weather capabil- ity including day and night observation. Radar Multispatial capability backscatter is sensitive to a different set of proper- Satellite sensors, over the years have pro- ties like surface roughness, slope and dielectric gressed, in terms of spatial resolution in addition property of surface material. Radar image has to many other sensor improvements. Today 1-m unique characteristics of its own. The shadow ef- resolution data are available along with other reso- fect, for example, is useful for terrain analysis. lutions ranging from 2 m to 1000 m or more by The subtle elevation differences, which are not di- satellites launched by space faring nations. While rectly perceived in optical remote-sensing image, this range provides opportunity of multispatial are highlighted in radar image. Such subtle relief capability, the need for selecting appropriate reso- changes may have significance in neotectonics or lution data is imperative. Broadly, for regional may represent a boundary condition. The inter- mapping, low resolution data may be adequate pretation of radar image is based on form, topog- whereas for understanding landscape ecology of a raphic texture and pattern, topographic position, small area high-resolution data may be appropri- pseudo-3D presentation of form (slope) and re- ate. Time, economy and objective of study have to gional geomorphic context.

Fig.1. Satellite data showing Doon Valley and surroundings. 54 GEOMORPHOLOGY

One of the most commonly using applications levees are invariably occupied by settlements, of radar imagery in the Indian context is mapping being higher in elevation whereas the of flood and cyclone affected areas. The change backswamps have agriculture/aquatic vegeta- brought about by devastating floods in Brah- tion. Indo-Gangetic plain is a typical example. maputra river and changes in coastal configura- Association of features, an important element of tion of Orissa coast in the after math of super- image interpretation, contributes also to a cyclone Orissa coast in October 1998 are good ex- proper understanding of the landform. Vegeta- amples. tion, land use, drainage, mode of clustering of settlements together help in proper interpreta- Geomorphology and landscape ecology tion of geomorphology. According to Verstappen (1977, pp.138) “….. Aerial photos have been historically used to Natural and cultural landscapes are composed capture ground features. Largely used in the be- of a number of elements or components which ginning after World War II for geological map- are mutually interrelated through a frame work ping, it was soon realized that geomorphological of landscape ecology”. Many authors (Verstap- understanding of terrain features is so direct pen 1977) have described segmentation of ter- from aerial photos. Several techniques of inter- into distinct but unique character. The pretation of aerial photos were developed. The land system concept of CSIRO in Australia is a basic elements which help in image interpretation good example. The land systems are units hav- are shape, size, tone, texture, slope/relief, drain- ing unique characters of landform, type, age and association of features. These are related vegetation and land use. This can be extended to the scale of aerial photos. The scales of com- to other characters like condition, monly used aerial photos vary from 1:10,000 to slope etc. The close linkage between the land- 1:50,000 although for very large scale mapping, form and other ecological factors as exist in the scales larger than 1:10,000 are used and for a terrain are reflected in the aerospace imagery quick reconnaissance surveys scales smaller than through various degrees of correlation in the 1:50,000 are used. The advantage of aerial photo distribution pattern. For example, the point is that they provide stereoscopic view, enabling bar/natural levee/backswamp pattern of a typi- the interpreter to understand the genesis of land- cal fluvial landscape evidently has a strong cor- form in addition to amenability to measurement relation between land use and landform. The of slopes, heights etc. Although black & white

Fig. 2. Horizontal profile along the points X and Y as shown in Fig. 1. RAO 55 aerial photos are used in majority of cases, infra- Case studies , color, thermal and radar images from aerial platform are also used for specific purposes. Three case studies are presented here to illus- However, the mechanism of acquisition, storage, trate the efficacy of remote sensing in environ- retrieval of images and their interpretation, is mental geomorphological interpretation including different for each type of image (Verstappen landform ecological correlation. 1977). The ITC system of geomorphological sur- vey is ideally suited for aerial photo interpreta- Doon valley tion, although the principles of survey remain The Doon valley and surroundings (Figs. 1 & valid for space imagery. 2), in the foothills of western Himalayas, is geo- Interpretation of remotely sensed images logically very young, representing upper Tertiary from space platforms for geomorphological under- , namely the Siwalik group of rocks and standing is rather direct as the main object of in- younger gravel beds. It is a high rainfall area re- terpretation is landform itself, which manifests ceiving 2300 mm year-1. A profile from south (X) itself in its form. Deduction is required unlike in to North (Y) in Fig. 2 describes the relationship of other themes although for understanding the geomorphology, structure, geology and land use/ processes it may be employed usefully. The syn- vegetation. Along the section X to Y, wide alluvial optic view of a large area in a single view enables plains partly under agriculture and partly under understanding of interrelationship of various ter- forest cover followed by abruptly rising Siwalik rain features. hills with sharp ridge separating drainage flowing

Fig. 3. Satellite data showing Mahanadi Brahmani delta system and surrounding coastal landforms. 56 GEOMORPHOLOGY north and south arisen. North of the ridge low Si- south facing ones having grasses. As the size of walik hills have a prominent but short upper and boulder increases, towards the crest of the ridge we lower piedmont slopes abutting against long pied- see an area of intense dissection with high drainage mont fan slopes of northern part of Doon valley on density. There is a natural disturbance for the which the township of Dehradun is located. growth of dense forest because of scarp recession due to headward erosion of streams which is more South Siwalik ridge rampant in the south side as compared to the north side. Before the Siwaliks rise abruptly from the plains, two different piedmont slopes arisen. The North of Siwalik ridge lower piedmont is a gentle slope consisting of grav- els and sand covered by rich alluvial soils. The up- The north side morphology is different with a per piedmont consisting coarse gravels with steeper short length of the upper Siwalik gently dipping north and merging with upper piedmont. The area footslopes is conducive for high recharge and enable for artesian conditions at the junction with lower has high and is covered by dense piedmont, thus making the lower piedmont a rich mixed Sal forest. In contrast, the lower piedmont slopes are covered by pure Sal forest as the brick area for agriculture. Before agriculture was intro- duced this area also had Sal mixed forest. The up- red color indicates. Streams draining the slope per piedmont has two components, namely a foothill join axial streams flowing west and east to the north of which the northern part of Doon Valley is zone where due to coalescence of fan deposits from several streams contains coarse boulders, gravels predominantly covered by Doon fans which have and sand admixed with silt and . This zone is a long slopes having urban and agriculture land use. Dehradun is situated on one such big alluvial fan. high recharge zone. The lower half of the upper To the east of Dehradun the water drains to the piedmont has medium coarse material and rela- tively gentler slope. The entire upper piedmont is river Ganges and to the west into the Yamuna river. These Doon fans are having relict hills con- covered by deciduous mixed Sal forest, Sal dominat- sisting of older boulder bed (Lamgha boulder bed ing. The structural hills of middle Siwalik rocks rise abruptly over the upper piedmont because of a of Rao 1977). These hills are once again covered by Sal forest. The Doon fans have (not along sec- foothill . These structural hills are controlled tion line) patches of Sal forest particularly in the morphologically by the lithology, the southern part consisting of alternating sandstone and shale over- western part indicating, the original ecological conditions, modified by human settlements. The lain by massive sandstone, which have grassy slope high relief of Lesser Himalayas consists of denuda- facing south and open mixed Sal forest on northern aspects. These are overlain by upper Siwalik gravel tional hills with steep slopes, which are sparsely covered by vegetation, which is totally different and boulder beds with intermittent clay layers. The transition between middle Siwalik and upper Si- from Siwalik hills. The case study demonstrates walik is seen with beautiful flat iron dip slopes, the how landform and ecological relationship exists and perceived holistically through satellite image north facing dip slopes having typical Sal forest and interpretation.

Fig. 4. Horizontal profile along the points X and Y shown in Fig. 3. RAO 57

Mahanadi Brahmani delta system tion of spits and bars is due to long shore drift- ing is evident and these spits are mostly covered This area, in the east coast depicts landform by Casuarina as the spite consist of sands. In resulting due to interaction of sea and land the bays, a healthy vegetation is seen (Figs. 3 & 4). The area is largely covered by (Porwal & Roy 1991; Roy et al. 1991). North of Mahanadi and Brahmani river Delta in the Brahmani river estuary NW-SE trending beach northeast and Chilka lake in the south. ridges occur, the ridges having Casuarina vege- Mahanadi and Brahmani river delta is associ- tation and swamps having mangrove vegetation. ated with estuarine bays, spits and bars, beach The current activity indicates the coast is pro- ridges and swamps. A profile from X to Y Fig. 4 grading with abundant covering from describes the landform- land cover relationship. hinterland as seen by sediment plumes near Y in Towards south is Chilka lake, a former arm of the section. the sea, now undergoing filling with sediments from hinterland. The typical delta of Mahanadi Kanha national park area with multiple branches emanating from one sin- gle channel, one of which also debouches into Geomorphologically this area in Central India Chilka lake. The lake has weeds in the northern (Figs. 5 & 6) comprises of structural and denuda- part; the cross profile of the delta is convex up. tion hills with attendant valleys and remnants of While agriculture predominates most of the plantation surfaces, which are locally known as delta area, the area adjacent to coast is swampy ‘Dadars’. Lateritic caps, which add to the interpre- having degraded mangrove vegetation. Forma- tation that the area has undergone plantation

Fig. 5. Satellite data showing Kanha National Park and surrounding. 58 GEOMORPHOLOGY usually, underlie these flattop Dadar. A profile and GIS provides unlimited applications for geo- across the park from X to Y Fig. 6 is described morphological studies. here. The streams are seen to be meandering in the area. The fact that remnants remarks of old References plantation surfaces (Dadar) occur gives a possibil- ity of river entrenchment which is indicative of the Fairbridge, R.W. 1968. The Encyclopedia of Geomorphol- area having undergone uplift after undergoing re- ogy: Encyclopedia of Earth Science Series. Reinhold gional plantation. The river also shows structural Book Corporation. New York, Amsterdam, London. control. The complex structure of old geologic for- Lillesand, T.M. & R.W. Kiefer. 2000. Remote Sensing mation consisting of gneisses and schists is show- and Image Interpretation. Fourth Edition, John ing effects of denudation as well as structural im- Wiley & Sons, Inc. New York. prints with the result that from the alluvial plain Porwal, M.C. & P.S. Roy. 1991. Attempted understorey to high points in relief we can see gradual transi- characterisation using aerial photographs in Kanha tion from undulating plain to denudational hills to National Park (Madhya Pradesh) India. Environ- plateau above which structural forms persist. The mental Conservation 18: 45-50. vegetation pattern has adjusted to topography, Rao, D.P. 1975. On the origin of Renuka lake. Photonir- slope, moisture and climate. The profiles of vege- vachak (Journal of Indian Society of Remote Sens- ing) 3:37-41. tation cover change thus indicate that the mor- Rao, D.P. 1977. A note on recent movements and origin phology including micromorphology has strong of some piedmont deposits of Dehradun valley. control on ecology. Photonirvachak (Journal of Indian Society of Re- The unplanned and indiscriminate use of land mote Sensing) 5: 35-42. has caused tremendous loss in natural resources. Rao, D.P. 1978. Utility of landsat coverage in small The technology development scenario and user re- scalegeomorphological mapping - some examples quirements during the last decade have necessi- from India. Photonirvachak (Journal of Indian Soci- tated the launch of second generation remote sens- ety of Remote Sensing) 6: 49-56. ing satellites. The use of this tool with the GPS

Fig. 6. Horizontal profile along the points X and Y as shown in Fig. 5. RAO 59

Roy, P.S., D.N. Pant & S. Jonna. 1991. Evaluation of Van Westen, C.J. 1994. Geographical information sys- grasslands and spectral reflectance relationship to tems in hazard zonation: a review with its biomass in Kanha National Park (M.P.). Geo- examples from the Andes of Colombia. pp. 135-166. carto-International Journal of Remote Sensing 6: 39- In: M.F. Price & D.I. Heywood (eds.) GIS Applica- 45. tions for Mountain Areas. Taylor and Francis, UK. Sabins, F.F., Jr. 1997. Remote Sensing – Principles and Verstappen, H.Th. 1977. Remote Sensing in Geomor- Interpretation. 3rd ed., W.H. Freeman, New York. phology. Elseviers, Amersterdam.